Besides /proc/self|<pid>, files under /proc/thread-self and /proc/self|<pid>/task/<tid> also expose host information to the guest program. This patch adds them to the hijack infrastracture. Note that is_proc_myself() does not check if the <tid> matches the current thread and is thus only suitable for procfs files that are identical for all threads in the same process.
Behavior verified with guest program: long main_thread_tid; long gettid() { return syscall(SYS_gettid); } void print_info(const char* cxt, const char* dir) { char buf[1024]; FILE* fp; snprintf(buf, sizeof(buf), "%s/cmdline", dir); fp = fopen(buf, "r"); if (fp == NULL) { printf("%s: can't open %s\n", cxt, buf); } else { fgets(buf, sizeof(buf), fp); printf("%s %s cmd: %s\n", cxt, dir, buf); fclose(fp); } snprintf(buf, sizeof(buf), "%s/maps", dir); fp = fopen(buf, "r"); if (fp == NULL) { printf("%s: can't open %s\n", cxt, buf); } else { char seen[128][128]; int n = 0, is_new = 0; while(fgets(buf, sizeof(buf), fp) != NULL) { const char* p = strrchr(buf, ' '); if (p == NULL || *(p + 1) == '\n') { continue; } ++p; is_new = 1; for (int i = 0; i < n; ++i) { if (strncmp(p, seen[i], sizeof(seen[i])) == 0) { is_new = 0; break; } } if (is_new) { printf("%s %s map: %s", cxt, dir, p); if (n < 128) { strncpy(seen[n], p, sizeof(seen[n])); seen[n][sizeof(seen[n]) - 1] = '\0'; ++n; } } } fclose(fp); } } void* thread_main(void* _) { char buf[1024]; print_info("Child", "/proc/thread-self"); snprintf(buf, sizeof(buf), "/proc/%ld/task/%ld", (long) getpid(), main_thread_tid); print_info("Child", buf); snprintf(buf, sizeof(buf), "/proc/%ld/task/%ld", (long) getpid(), (long) gettid()); print_info("Child", buf); return NULL; } int main() { char buf[1024]; pthread_t thread; int ret; print_info("Main", "/proc/thread-self"); print_info("Main", "/proc/self"); snprintf(buf, sizeof(buf), "/proc/%ld", (long) getpid()); print_info("Main", buf); main_thread_tid = gettid(); snprintf(buf, sizeof(buf), "/proc/self/task/%ld", main_thread_tid); print_info("Main", buf); snprintf(buf, sizeof(buf), "/proc/%ld/task/%ld", (long) getpid(), main_thread_tid); print_info("Main", buf); if ((ret = pthread_create(&thread, NULL, &thread_main, NULL)) < 0) { printf("ptherad_create failed: %s (%d)\n", strerror(ret), ret); } pthread_join(thread, NULL); return 0; } Signed-off-by: Shu-Chun Weng <s...@google.com> --- linux-user/syscall.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 8367cb138d..73fe82bcc7 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -6968,17 +6968,57 @@ static int open_self_auxv(void *cpu_env, int fd) return 0; } +static int consume_task_directories(const char **filename) +{ + if (!strncmp(*filename, "task/", strlen("task/"))) { + *filename += strlen("task/"); + if (**filename < '1' || **filename > '9') { + return 0; + } + /* + * Don't care about the exact tid. + * XXX: this allows opening files under /proc/self|<pid>/task/<n> where + * <n> is not a valid thread id. Consider checking if the file + * actually exists. + */ + const char *p = *filename + 1; + while (*p >= '0' && *p <= '9') { + ++p; + } + if (*p == '/') { + *filename = p + 1; + return 1; + } else { + return 0; + } + } + return 1; +} + +/* + * Determines if filename refer to a procfs file for the current process or any + * thread within the current process. This function should only be used to check + * for files that have identical contents in all threads, e.g. exec, maps, etc. + */ static int is_proc_myself(const char *filename, const char *entry) { if (!strncmp(filename, "/proc/", strlen("/proc/"))) { filename += strlen("/proc/"); if (!strncmp(filename, "self/", strlen("self/"))) { filename += strlen("self/"); + if (!consume_task_directories(&filename)) { + return 0; + } + } else if (!strncmp(filename, "thread-self/", strlen("thread-self/"))) { + filename += strlen("thread-self/"); } else if (*filename >= '1' && *filename <= '9') { char myself[80]; snprintf(myself, sizeof(myself), "%d/", getpid()); if (!strncmp(filename, myself, strlen(myself))) { filename += strlen(myself); + if (!consume_task_directories(&filename)) { + return 0; + } } else { return 0; } -- 2.23.0.rc1.153.gdeed80330f-goog